This invention relates to pyrocarbon and to processes for depositing pyrocarbon coatings on substrates in a fluidized bed. More particularly, the invention relates to processes for depositing pure, unalloyed pyrocarbon having improved physical properties on substrates being levitated in a coating region along with a bed of small particles and also to pyrocarbon having improved mechanical properties heretofore obtained only in silicon-alloyed pyrocarbon structures.